The present application is the national stage under 35 U.S.C. 371 of international application PCT/SE00/00339, filed Feb. 18, 2000 which designated the United States, and which international application was published under PCT Article 21 (2) in the English language.
The present invention relates to an agent for use in transplanting a tissue or an organ from a donor to a receiver with the need of such an organ.
Transplantation of tissues (organs) is an area within the health care system undergoing a fast development and with an increasing number of transplants per year. There is definitely a very limited supply of tissues (organs) and the tissues (organs) are under normal circumstances available only a few hours before the transplantation. The limiting factor is the time that is available after the removal of the tissue(organ) from the donor and until it is function in the receiver of the tissue(organ). The time factor is thus very critical and requires night time operations (day time operations are not possible with a few hours notice), ambulance and air transportation and several ongoing operations to prepare the receivers which could be up to 5-6 different patients at different hospitals. The receiver operation can take up to 12 hours in the case of a liver transplantation.
In the following specification and the claims the term tissue is intended to comprise all tissues, organs and cells that can be transplanted. These terms are used interchangeably in this specification.
There are three problematic steps in transplantation, all involving potential problems of oxidative stress, i.e. the quality of the tissue (organ), i.e. survival.
I. The time at intensive care for the donor. This means exposure to oxygen (higher percentage and pressure) and failure of a number of normal body functions.
II. The time after the removal to the function in the receiver. This is very critical. The organ is chilled to +4xc2x0 C. and washed with a solution for storage and transport, eg. a UW-solution. After the removal, the organ is stored in said solution on ice. UW-solution is saline with additions to maintain the salt-balance and avoid tissue damage.
III. In the receiver there are several critical steps, the first being re-perfusion, i.e. to turn on the blood flow again: Re-perfusion causes a massive oxidative burst. Secondly there are immune reactions and long-term effects of the transportation (partial cell death of certain groups of cells).
The optimization of the transplantation procedure is of great importance and several receivers life depends on that the whole procedure is very efficient and that the organs are not destroyed in this process.
Oxidative stress occurs when there is an imbalance between oxidants and free radicals versus protective mechanisms like SOD enzymes, catalase, DNA-repair etc. Oxidative stress is a major or minor part of most diseases, examples are: heart/brain infarctions, trauma, sepsis, arthritis, diseases of the immune system, cancer, inflammation, infection and CNS-diseases. In all these diseases the oxidative stress leads to cell damage and the outcome is dependent upon if the organ can survive the acute phase, a situation that is obvious during infarction but also relevant for chronic diseases like arthritis with a constant oxidative stress of the joints.
The present invention relates to the use of an agent in the transplantation of an organ from a donor to a receiver with the need of such an organ. The agent according to the present invention is suitable to use in different steps which are related to the transplantation procedure. Thus, the agent can be a) administered orally, intraperitoneally or intravenously to a donor from which an organ shall be removed; b) the agent can be added to a solution in which the organ is to be stored and transported (eg. a UW solution) c) the agent is administered orally, intraperitoneally or intravenously to the receiver of the organ, i.e. the patient in which the organ shall be implanted.
In tissue degradation several mechanisms are involved, since oxidative stress affects tissues by several different mechanisms, viz. by oxidation of proteins, lipids-and DNA. During the oxidation of proteins and lipids of the tissue all structures are severely damaged by free radicals a consequence of which is loss of function which leads to cell death and ultimately to the death of the tissue.
According to the present invention it has surprisingly been found that by using an agent, which is a substituted indoloquinoxaline of the following general formula I, the organ which is transplanted is protected against degradation caused by oxidative stress during the whole sequence of steps which are necessary for carrying out a transplantation.
The agent which according to the present invention is to be used in connection with the transplantation is a compound of the following general formula I 
wherein R1 represents hydrogen or one or several, preferably 1 to 4, similar or different substituents in the positions 1-4 and/or 7-10, selected from halogen, preferably Br, lower alkyl/alkoxy group having not more than 4 carbon atoms, tri-fluoromethyl group, trichloromethyl group; and in one of the positions 7-10 R1 can be a hydroxyl group;
X is a groupxe2x80x94(CH2)nxe2x80x94R2, wherein R2 represents a nitrogen containing basic residue such as NH2, NHR4 or NR5R6, wherein R4, R5 and R6 independently are lower alkyl or cycloalkyl and n is an integer of from 1 to 4 and R3 represents hydrogen, lower alkyl/cycloalkyl group having not more than 4 carbon atoms, and the physiologically acceptable addition products of the compounds with acids and halogen adducts, preferably adducts with iodine, iodine monochloride or iodine monobromide.
R1 is preferably selected from hydrogen and lower alkyl groups, especially methyl. More preferably R1 is methyl in positions 2 and 3 and hydrogen in the other positions.
A compound which proven to be especially effective is the compound of the following formula II 
Such compounds and their preparation are described in EP patent 0238459 and U.S. Pat. No. 4,990,510 which are incorporated herein by reference.
The use of the agent according to the present invention in these three applications[I, II and III)] is prophylactic for preventing tissue damages during the transplantation. Thus, by treating the tissue which shall be transplanted in situ the protective mechanisms are activated which secure the survival of the organ. The agent according to the present invention thus, acts so that the tissue degradation mechanisms are down-regulated/blocked which means that the period for storage and transport of the tissue is prolonged. This extension of time means that a higher number of countries and regions can be involved in the exchange of tissues for transplantation. Thus,when tissues are transplanted they are submitted to tissue degradation if not the DNA/protein/enzymes etc. of the tissues are protected against degradation.
General tissue damage can be measured by means of measuring metabolic capacity or tissue function. Thus, for a tissue like the liver the capacity to reduce lactate levels of the blood and produce bile are such markers(indicators). Since DNA controls the whole function of the cell and thereby the whole tissue, oxidation of DNA is also a risk factor for survival. Oxidation of DNA is also a promutagenic event.
In the DNA oxidation cells are exposed to reactive oxygen. During this oxidative stress hydroxyl and superoxide radicals oxidize dG which leads to 8-OH-dG formation which is a promutagenic event which leads to strand breaks, base-substitutions, ring opening of dG and/or affects DNA-methylation. (dG is deoxyguanosine, one of the bases of DNA).
The agent of formula I represents a potentially important agent to increase the survival of cells and organs during transplantation by dramatically reducing the oxidative stress. The agent of formula I is a non-toxic substance in vivo and protects the tissues in two ways. First there is a blocking of oxidative enzymes (oxidases) that generate oxidants. Secondly there is a gene-regulation that activates the general cell-defense. Thus, the agent of formula I does not work as an anti-oxidant but activates the defense mechanisms of the cell to up-regulate the protection for oxidative stress.